UPDATE, Wednesday, 3 September, 4:50 a.m. ET: The U.S. government has confirmed the brutal video showing the beheading of U.S. jounalist Steven Sotloff is authentic.

US National Security Council spokesperson Caitlin Hayden said in a statement to the BBC: "The U.S. Intelligence Community has analyzed the recently released video showing U.S. citizen Steven Sotloff and has reached the judgment that it is authentic."

The radical group the Islamic State released a video on Tuesday showing the beheading of a second American journalist.

In the two-camera video, titled "A Second Message to America," Steven Sotloff, wearing an orange jumpsuit, can be seen kneeling in the desert in front of a man dressed in black, holding a serrated knife.

Image: Screen grab

Sotloff, who appears remarkably composed, then says, "I am Steven Joel Sotloff. I am sure that by now you know exactly who I am and why I am appearing before you." He then recites a propaganda message seemingly prepared for him by his captors. Afterward, his captor says, "I'm back, Obama, and I'm back because of your arrogant foreign policy against the Islamic State," in what sounds like a London accent.

The footage closely resembles a video depicting the beheading of American journalist James Foley two weeks ago. The executioner in that video also appeared to have a London accent, though it was unclear if this was the same man.

In the Foley video, Sotloff was dragged before the camera toward the end. The masked man said Sotloff’s life depended in part on whether the United States would stop bombing Islamic State militants in Iraq.

The Islamic State threatened to kill a third man in the video released Tuesday. He was identified as David Cawthorne Haines.

The Islamic State is also holding at least two more western prisoners, both of whom are American. One captive is an unnamed 26-year-old woman who, like Haines, is a humanitarian worker. She was taken captive on Aug. 4, 2013, and militants are reportedly demanding a $6.6 million ransom to spare her life. The radicals’ other prisoner is an unidentified man.

The video of Sotloff's killing was first confirmed Tuesday by the SITE Intel Group, which monitors extremist networks.

Speaking to reporters on Tuesday afternoon, White House press secretary Josh Earnest said the U.S. had not yet confirmed the video, but intelligence officials will analyze it to determine its authenticity. He added that the U.S. had tried to rescue Sotloff.

"This is something that the administration has obviously been watching very carefully since this threat against Mr. Sotloff's life was originally made a few weeks ago," Earnest said. "The United States, as you know, has dedicated significant time and resources to try and rescue Mr. Sotloff."

Earnest also expressed his condolences to Sotloff's family.

"Our thoughts and prayers, first and foremost, are with Mr. Sotloff and Mr. Sotloff's family and those who worked with him."

Sotloff’s mother released a video of her own last week pleading for her son’s life. In it, she addressed Islamic State leader Abu Bakr al-Baghdadi by his self-proclaimed title, caliph.

“I ask you please to release my child,” Shirley Sotloff said. “I ask you to use your authority to spare his life.”

The Sotloff family was aware of the video Tuesday and was grieving, a family spokesman told the Associated Press.

Sotloff, a 31-year-old journalist who has worked for several media publications including Time, vanished in Syria around one year ago. He’s written about the life of Syrian refugees in a tent city, the violent assault on the American consulate in Benghazi, Libya and attacks on Benghazi police.

Steve Sotloff lived in Yemen for years, spoke good Arabic, deeply loved Islamic world.. for this he is threatened with beheading.

Eliot Higgins, a blogger better known for his online alias Brown Moses, claimed to have identified the location where the Islamic State executed James Foley by looking at the position of the shadows of the journalist and his murderer, as well as details visible in the video that he was able to match with satellite images. After looking at the video of Sotloff's beheading, Higgins told Mashable that it doesn't appear to have been filmed in the same area.

On Twitter, Higgins added that it took him a couple of days to narrow down the location of Foley's execution, and that based on what he has seen so far, Sotloff's video appears to have been shot in a "different location."

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